This nonprovisional application claims priority under 35 U.S.C. xc2xa7119(a) from German Patent Application No. 199 54 489.1 filed in Germany on Nov. 12, 1999, which is herein incorporated by reference.
1. Field of the Invention
The present invention relates to a circuit for operating an alternating current high pressure gas discharge lamp for a motor vehicle, having a ballast, a starter, a symmetrical lamp filter and a high pressure gas discharge lamp at least partially surrounded by a reflector, the symmetrical lamp filter being arranged between the high pressure gas discharge lamp and the starter circuit, having a filter capacitor arranged in parallel with the high pressure gas discharge lamp and a reactance coil in the connecting lines between this parallel circuit and the starter circuit, and having two lamp power supply lines at the input of the starter circuit.
2. Description of the Background Art
The high pressure gas discharge lamps usually used in motor vehicles, namely D1 and D2 lamps, have an asymmetrical design with regard to their power supply connections. The feedback line together with the reflector forms a capacitance of approx. 2 to 3 pF; the reflector forms an equally large capacitance with the vehicle. Interference pulses on the feedback line are thus fed as capacitance into the vehicle electric system by way of the vehicle chassis and are difficult to filter out in the starter.
It is therefore an object of the present invention to prevent interference pulses from being fed into the vehicle chassis and the vehicle electric system.
This object is achieved according to the invention by arranging a capacitor between the reflector and one of the lamp power supply lines.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.